1. Field of the Invention
The present invention relates to a phase shift mask that improves resolution of a transcription pattern by applying a phase difference between exposure lights permeating a mask. The present invention also relates to a phase shift mask blank material. The present invention particularly relates to method for manufacturing a halftone type phase shift mask blank and method for manufacturing a halftone type phase shift mask.
2. Description of the Related Art
In recent years, high resolution and focal depth, which are two important characteristics required for photolithography, have opposed relation, and it is known that actual resolution can not be improved only by high NA (Numerical Aperture) of a lens of an exposure device and shortening of wavelength (Semiconductor World December 1990, and Applied physics Vol. 60, November 1991, the Japan Society of Applied Physics, etc.).
Under the circumstances, phase shift lithography is viewed as a photolithography technique of the next generation. The phase shift lithography is a method improving resolution of light lithography by change of only a mask without change of an optical system, and resolution is greatly improved using interference of mutual permeated light by applying phase difference between exposure light permeating a photo mask.
The phase shift mask is a mask having both light strength information and phase information, and various kinds, such as Levenson type, auxiliary pattern type, self matching type (edge emphasis type) and so on are known. This phase shift mask is complex in structure and requires technical expertise to produce, compared with the conventional photo mask having only light strength information.
As one of the phase shift masks, a so-called half tone type phase shift mask has been developed recently.
Since the half tone type phase shift mask has two functions, a shielding function so that a translucent portion virtually shields exposure light and a phase shift function so that a translucent portion shifts phase of light (usually reverse), it is needless to form a shielding film pattern and a phase shift film pattern individually so that the construction is simple and production is easy.
As shown in FIG. 1, the half tone type phase shift mask is constructed of a light transparent portion (transparent substrate exposure portion) 200 permeating strong light substantially contributing to exposure and a translucent portion (a light shielding portion and a phase shifter portion) 300 transmitting weak light actually not contributing to exposure (See FIG. 1(a)). Phase of light permeating the light transparent portion is shifted so that phase of light permeating the translucent portion becomes actually reversed against phase of light permeating the transparent portion (See FIG. 1(b)). Light passing near the boundary portion of the light translucent portion and the light transparent portion, and getting in the other region by diffraction phenomenon cancel each other so that light strength at the boundary is made almost zero and, by contrast, resolution of the boundary is improved (See FIG. 1(c)).
The light translucent portion of the above-mentioned half tone type phase shift mask is needed to have the most suitable values required for both the light transmission factor and phase shift quantity.
The applicant of the application has previously investigated a phase shift mask for realizing the most suitable values required at a single layer light transparent portion (Japanese Patent Laid-Open No. 332152/1994).
The light translucent portion of the phase shift mask is constructed by a thin film consisting of metal, such as molybdenum and the like, silicon, and oxygen, as a main component. Concretely, these materials are, for example, material including oxygen, molybdenum, and silicon (called MoSiO family material), and material including oxygen, nitrogen, molybdenum, and silicon (called MoSiON family material).
According to the construction, transmittance can be controlled by selecting the oxygen content or the content of oxygen and nitrogen, and the phase shift quantity can be controlled by thickness of the film. By constructing the light translucent portion with such material, the light translucent portion is constructed with a single layer film consisting of one kind of material, and the film forming process is simplified and one etching medium can be used, as compared with construction of multi layers consisting of different materials, so as to simplify the manufacturing process.
The applicant of the application has previously investigated a phase shift mask having a light translucent portion with improved characteristics of acid resistance, light resistance, conductivity, and so on (Japan Patent No. 2966369).
The light translucent portion of the phase shift mask is constructed by a thin film including material consisting of metal such as molybdenum and the like, silicon, and nitrogen as a main component. Concretely, this material includes nitrogen, molybdenum, and silicon (called MoSiN family material).
However, the following problems result in the above-mentioned conventional MoSiN family half tone type shift mask and the method for manufacturing the same.
That is, as described above, in designing the film material of the translucent portion of the phase shift mask, control of phase angle and transmittance is carried out by selecting contents components, and the transmittance is adjusted by setting contents of oxygen and/or nitrogen. However, because the transmittance must be adjusted only by nitrogen using MoSiN family material, fine adjusting of transmittance to obtain the desired transmittance is difficult. Then, although a method further adding oxygen is considered, rate of change of transmittance becomes large by adding oxygen, fine adjusting is difficult, and further chemical resistance and light resistance against exposure light are worse than only using nitrogen.
A requirement for chemical resistance (acid resistance and alkali resistance) to the washing liquid of the mask is severe as shortening wavelength of exposure wavelength so that higher chemical resistance is required.
Further, since fine working of a pattern is advanced recently, internal stress of the translucent film is increased. However, there is a problem that film of low internal stress in absolute value is not always obtained when the composition is adjusted to obtain the designated transmittance and phase angle.
The invention is carried out in view of the above-mentioned problems, and an object is to provide a method for manufacturing a phase shift mask blank or a method for manufacturing a phase shift mask having the designated phase angle and transmittance, and having a translucent film or a light translucent portion superior in chemical resistance, light resistance, and film characteristics such as internal stress.
To achieve the above-mentioned object, the invention has the following aspects.
An aspect of the invention is a method for manufacturing a half tone type phase shift mask blank having a translucent film on a transparent substrate, wherein thermal treatment of the translucent film is implemented at more than 150xc2x0 C. after forming the translucent film including at least one layer of thin film comprising nitrogen, metal, and silicon as a main component on said transparent substrate.
Another aspect of the invention is a method for manufacturing a half tone type phase shift mask blank having a translucent film on a transparent substrate, wherein thermal treatment of the translucent film is implemented at more than 380xc2x0 C. after forming the translucent film including at least one layer of thin film including oxygen and/or nitrogen, and silicon on said transparent substrate.
Yet another aspect of the present invention is a method for manufacturing a photo mask having thin film of one layer or multi layers for forming a pattern on a transparent substrate, wherein thermal treatment is implemented so that flatness change quantity at before and after film forming of thin film having said one layer or multi layers is less than 0.5 xcexcm after forming thin film of one layer or multi layers including at least one layer of thin film having compression stress on said transparent substrate.
Further, another aspect of the present invention is a method for manufacturing a half tone type phase shift mask having a pattern of a light translucent film patterned on a transparent substrate, wherein thermal treatment of the pattern of the translucent film is implemented at more than 150xc2x0 C. after forming the translucent film including.